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GaN-Based Isolated DC-DC Converter for Space Application

Fig. 1. Isolated dc-dc converter diagram.
The design of an isolated dc-dc zero voltage switching (ZVS) full-bridge converter using a current doubler synchronous rectifier on the secondary side to achieve high efficiency and high power density while abiding to circuit design constraints encountered in rad-hard applications is described in this paper. The prototype uses a combination of radiation-hardened parts and industrial-rated components with radiation-hardened equivalent packages to keep prototyping costs down and parts procurement under control. Fig. 1 shows a high-level block diagram for converter topology. The power stage uses hermetically packaged rad-hard GaN FETs from Freebird Semiconductor. Low-profile planar magnetics using discrete helical-windings arrangements were selected for the transformer, and required resonant and output inductors for the current doubler rectifier.
Hard-switched and ZVS phase-shifted modulation schemes are compared in terms of component stress, efficiency, and conducted electromagnetic interference. Design methodology for hard-switched and ZVS full-bridge converters, and magnetics design tradeoffs are presented. Also, the main challenges encountered in designing radiation hardened power converters and their effects on converter design choices are briefly discussed.

Fig. 2. Isolated dc-dc converter diagram.
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